Coating



Patented Sept. 3,1940

COATENG James A. Mitchell, Kenmore, N. Y., assignor to E. I. du Pont deNemours & Company, Wilmington, Del., a corporation of Delaware NoDrawing. Application September 8, 1937, Serial No. 162,887

21 Claims.

non-adherent at moderately elevated temperatures.

Thin transparent sheets and films of nonfibrous cellulosic materialscontaining moisture proof coatings are well known as wrapping tissue. Ingeneral, the coatings of such sheets and films comprise a film-formingconstituent such as a cellulose derivative or a resin, amoistureproofing agent such .as a wax, a blending agent such as a resin,and a plasticizer. Such moistureproofing coating compositions andmethods for compounding and applying the same are disclosed in detail 20in the U. S. Patent No. 1,737,187 'to Charch and Prindle and FrenchPatent No. 718,440 to Charch.

Difficulty has long been experienced .in the handling and storing ofsuch sheets and films because of their lack of slipperiness and theadherence of 25 contiguous sheets to each other. These diificulties aredue to at least two factors. that some of the constituents of themoistureproofing composition may be inherently tacky. A second factor isthat the surfaces of these sheets are so smooth that, when they lie inclose juxtaposition, they have a tendency to exclude air from betweenthem, thus causing a vacuum action which renders it very difiicult toseparate the sheets, and at the same time to increase the area 35 ofcontact, thus increasing the coefiicient of friction. This smoothness isnot overcome and in fact is accentuated by the ordinary constituents ofthe moistureproofing composition, particularly the moistureproofingagent, since it apparently 40 forms a smooth continuous phase in orderto prevent the passage of moisture.

Furthermore, it has been observed that these difiiculties are greatlyaugmented by a slight rise in temperature. A sheet which provesperfectly satisfactory as to surface conditions at ordinary roomtemperatures may become very tacky and unmanageable when stored inheated places or when subjected to abnormally high room temperatures.Similar conditions have been found to 50 arise in the use of automaticwrapping machinery. As long as such wrapping tissue is manually appliedto packages, a slight degree of stickiness and frictional resistance,while an inconvenience, is of no considerable consequence. It becomes ofextreme importance, however, when such adher- One factor is ence andfrictional resistance is increased by the transmission of heat or theheat developed by friction in an automatic machine. It is found actuallythat a diiference of 1 or 2 may even cause a sticking of the material tosome part or 5 other of the machine -and completely foul its operation.Furthermore, due to the high speeds developed in such automaticmachinery, normal adherence and frictional resistance, even of the samedegree as can be tolerated in manual operation, are objectionable evenin the absence of a temperature rise.

An attempt has been made to overcome the adhesive tendency inherent inthese films by the use of a thin layer of talcum powder. This method hasthe disadvantage however that while it lessens the adhesion of thesheets, it stains the I film.

It has been suggested to incorporate small amounts of finely divided,insoluble materials, such as kaolin, aluminum hydroxide, titanium oxide,etc. in the moistureproofing coating compositions which are to beapplied to the film. ,Since this solid matter is in a very finelydivided form and since the coating bath is of relatively high viscosity,it is possibleto disperse these solid particles in the bath and applyevenly to the surface of the film. The presence of such solid matterproduces numerous points of separation between contiguous sheets instacked relation, or between the surface of the sheet and other smoothsurfaces, and thus insures good surface slip. However, the introductionof insoluble matter into the bath composition has several disadvantages.For one thing, it is very difficult to adequately disperse such solidmaterials without prolonged stirring and agitation and the dispersionmay not be stable over long periods of time or in all conditions ofoperation, so that pipe lines and apparatus may become clogged withsediment. Furthermore, it is not possible to filter the bath compositiononce the solid, insoluble material has been added, and filtration isoften necessary for the production of coating baths of the highestquality.

Another film defect from the use of such-solid insoluble .slip agentsused heretofore has been a lowering of the moistureproof quality whichis perhaps caused by interference with the continuity of the waxsurface. I

It is therefore an object of the present invention to produce amoistureproofing coating composition in which all constituents are insolution and which contains a solvent soluble slip agent which will besomewhat incompatible with the 5 other constituents of the coating inits final dry state.

It is another object of this invention to produce a transparent,non-fibrous sheet or film containing a moistureproofing coatingcomprising a. solvent soluble slip agent, which sheet or film will besubstantially non-adherent at elevated temperatures.

Other objects of the invention will appear hereinafter.

The objects of the invention may, enerally, be attained by the use of amoistureproofing coating composition containing a solvent soluble,metallic derivative of an organic compound, in which a metal issubstituted for a hydroxyl hydrogen, said derivative being completelysoluble in the liquid composition but which will not be completelycompatible with the other constituents of the composition in its finaldry state and which will therefore be present in a distinct phase fromthat of the main body of the coating.

Although any organic compound containing a metal substituted for ahydroxyl hydrogen can be used provided it has the above solubility andcompatibility requirements, the following test sets forth a convenientmethod for determining the requisite characteristics of the most usefulsubstances:

First, test the solubility of the substance in toluene at roomtemperature, or approximately 25 C. To function as a slip agent in thesense of this invention, it must be soluble to the extent of 1% or more.Second, place 0.5 gram of the material in a test tube, add 25 cc. ofacetone, place a stopper in the tube and shake. In this test also thetemperature of the solvent should be approximately 25 C. To function asa slip agent, the material must be partially or completely insoluble. Ifit is completely soluble, it will not function as a slip agent.

It is desirable that the slip agents separating in a distinct phase fromthe coating composition upon the removal of the solvent shall haveapproximately the same optical characteristics as the coatingcomposition itself. It therefore should preferably be substantiallycolorless (or at least colorless in the concentrations present in thefinal film) and have approximately the same index of refraction as thecoating composition, such that the resulting product will appeartransparent. The materials of the present invention are well suited forthispurpose. The following examples which are to be consideredillustrative and not limitative will assist in an understanding of theinvention.

The solvent soluble slip agents of the present invention shouldpreferably have the characteristic of raising the stick temperature(defined in detail below) of the coating composition above 55 C.

For the purposes of comparison and definition, the following test isused to determine the stick temperature: A web of the material to betested is moved across a table top and below a brass block with asurface of contact measuring 3 1: 1% inches, and weighing 500 grams, atthe uniform rate of 2 meters per minute. The temperature of the brass isslowly raised at the rate of about 7 C. per minute, and the frictionaldrag upon the film observed. This frictional drag at low temperatures isabout 50-100 grams; at some elevated temperature it increases suddenlyto several thousand grams, and the temperature at which this occurs istaken as the stick temperature.

Of the general class of organic compounds containing a metal substitutedfor a hydroxyl hydrogen, the most useful are those in which the hydroxyloxygen is attached to a carbon atom, and particularly metalcarboxylates. There also may be used metal phenolates, includingsalicylates, keto enolic compounds, etc. In the case of metalcarboxylates, the metal salts may be single or double. Among the singlesalts may be mentioned calcium, magnesium and cadmium butyl phthalates;zinc, barium, magnesium and calcium lauryl phthalates; calcium, andmagnesium cyclohexyl phthalates; aluminum, titanium, and barium benzoylbenzoates; aluminum, magnesium, zinc, and calcium cymoyl benzoates;aluminum tolyl benzoate; aluminum xylyl benzoate; aluminum, calcium,manganese, lead, magnesium, barium, cadmium, and strontium rosinates;calcium, aluminum, barium, strontium, and cadmiurn salts of modifiedrosin; calcium, zinc, and aluminum salts of Petrex resin; aluminum andcalcium salts of lauryl, butyl, and cyclohexyl half esters of Petrexresin; sodium ursolate; magnesium and calcium lauryl maleates oraluminum lauryl sebacate. Among the double salts may be mentionedzinc-aluminum rosinate, the aluminum salt of rosin and modified rosin,the aluminum salt of Petrex resin and modified rosin, and the aluminumsalt of phthalic acid and benzoyl benzoic acid. The use of these doublesalts for the present purposes are specifically claimed in copendingapplication to Daniel D.

Lanning, Serial No. 162,888, filed of even date herewith. Among the ketoenolic compounds may be mentioned aluminum acetyl acetone, zinc acetylacetone, calcium ethyl acetoacetate, aluminum ethyl acetoacetate, andaluminum ethyl malonate. The use of these keto enolic compounds for thepresent purposes are specifically claimed in U. S. A. Patent No.2,177,645 (Flint and Mitchell) The preferred slip agent of the presentinvention is the aluminum salt of modified rosin. From the examplesgiven in the table below, it will be observed that the stick temperatureobtained is very high. While other salts of this modified rosin, notablythe sodium and zinc salts, also give excellent surface qualities, thealuminum ion, being trivalent, has the advantage of giving salts ofseveral different degrees of basicity, depending upon the extent towhich it has been neutralized with the modified rosin, and thesedifferent compounds possess diiferent degrees of compatibility with thecoating composition preferred, so that not only can the type of compoundbe selected having the required effect upon the properties of thecoating composition, but also the concentration of this constituent maybe adjusted while still obtaining the maximum beneficial effect upon thesurface conditions. For instance, it has been found that the more basicsalts are less compatible with the coating composition so that if thecost of this material were an important factor, the amount requiredcould be kept at a minimum by using the most basic of the salts.However, if it were found that the plasticizing action was desirable andlarge quantities were therefore required, a more compatible form mightbe selected.

The following table gives the compositions of coating baths containingsalts of certain organic acids which have been found to give excellentsurface conditions and transparency when applied to transparentregenerated cellulose film. In each case the stick temperature, as abovedefined, will be found given. Parts are parts by weight.

The material listed as "Beckacite 1118 is a modified ester gummanufactured by Beck, Koller 8; Co. of Detroit, Michigan, and sold underthat trade-name.

silicon containing slip agents is represented by the following example.Silicon compounds, either organic such as ethyl silicate or inorganicsuch as silicon tetrachloride, which react with water or alcohol toprecipitate silicic acid may be added to lacquers containing waterand/or Table I-A Example 1 2 4 5 6 7 8 9 10 11 12 13 14 15 Constituentsin parts by weight Slip agent:

Magnesium but 1 hthalste 22 Bar umlsurylp t alate Barium benzoy benzoateMagnesium lauryl phthela Aluminum tolyl benzoate Calcium abietateCadmium abietate Barium abietate Sodium m nlafa Aluminum salt of Petrexacid .1 Aluminum monohydroxy benzoyl benzoate Nitrocellulose:

Plasticizer:

Dicyclohexylphthalate 22 0 22 15 17.1 396 36 44 29,4 39.7 16 l5Dlbutylphthalatc l5 17.1 9.8 l6 Ethyl benzoylbenzoate V 7.4

Resin:

Beckacite" 111s 12 2 Modified rosin Dowaxed gum damar...

Wax: Paraflin 3 3 Total solids; 100 100 Sticlrtemperature,"C. 69 90 7060 65 so 5 0 50 7 so 63 The material which is added as a slip agent tothe coating composition may also contribute other valuable properties tothecoating. For instance, a salt of rosin or modified rosin maycontribute to the body of the coating and serve to a certain, extent asa blending agent for the wax and the nitrocellulose. In other cases theslip agent added may aid in softening and plasticizlng the coating.Advantage may be taken of such properties to so modify the coatingcomposition as to effect a saving in some of the other ingredients suchas resin, blending agent,

, and plasticizer.

The slip agents of the present invention may flake, fiber or the like,is immersed in an aqueous solution of certain water soluble salts, suchas aluminum sulfate or zinc acetate. This is then followed by treatmentwith a solution such as ammonium hydroxide or sodium abietate whichprecipitates an insoluble slip agent on the pyroxylln structure. 7 Thetreated cellulose nitrate is' dried or dehydrated with alcohol and useddirectly in preparing lacquer solutions. The method is very effective inproducing moistureproof lacquers for regenerated cellulose filmexhibiting good slip properties. I

Still another general method of introducing 'spective solvents willvary:

alcohol to produce a finely divided dispersion of silicic acid or anintermediate product of hy-- producing lacquersdrolysis which iseffective in with good slip.

The slip agents of this invention must be completely soluble in thesolvent mixtures of the coating compositions, although they need not besoluble in every individual solvent of the solvent mixture. For thesolvents and solvent mixtures,

contain a cellulose derivative solvent and a wax solvent as well as asolvent for the resin and optionally a diluent. It is apparent that thesame solvent may serve for two or moreconstituents and indeed, it may bethat the cellulose derivative solvent will also be a wax solvent. Thesolvent mixture comprising 40-90% ethyl acetate, 10-50% toluene, and thebalance ethyl alcohol will usually be found to operate satisfactorily.Depending on the amount and nature of the cellulose derivative or of thewax, or ofthe slip agent, etc., the amount and nature of the re-Satisfactory solvents for the specific compositions are illustrated inthe accompanying examples.

In the preparation of a transparent, moistureproof wrapping tissue asuitable wax-containing composition comprising a cellulose derivativeand a solvent soluble slip agent may be applied to the desired base inaccordance with the methods known to the art. The solvents may beremoved, and the coated material subjected to an.

elevated temperature at least equal to the melting point of the wax,whence a clear, transparent,

moistureproof film may be obtained. The technique of this procedure isset forth in such patents as the Charch and Prindle Patent No.1,737,187.

While this invention has been described in terms of a coatingcomposition comprising a cellulose derivative and certain otherconstituents applied to a base film of regenerated cellulose or othermaterials, it will be understood that it is equally applicable to thepreparation of selfsustaining films of cellulose derivatives which areformed by extrusion, or casting, or other means from a solution in whichthe desired slip agent is more soluble than in the resulting film.

Moistureprooflng coating compositions may be used on variousnon-fibrous. transparent base sheets including sheets or films ofregenerated cellulose, whether they be made by the viscose process, thecuprammonium process, or by any other manufacturing technique; celluloseethers such as ethyl, benzyl or glycol cellulose; cellulose esters suchas cellulose nitrate or cellulose acetate; lowly etherified oresterified materials such as lowly etherified ethyl cellulose, lowlyetherified benzyl cellulose or lowly etherified glycol cellulose, andlowly esterified cellulose nitrate or lowly esterified celluloseacetate; gelatin, casein or the like.

In preparing moistureproofing coating compositions comprising solventsoluble slip agents, it has been found that the best results areobtained by limiting the relative amounts of the several constituents.The amount of film-forming constituent, for example, may vary from30-70%, or more of the total solids although in most instances 50-60% isto be preferred.

The solvent soluble slip agent may be present in amounts of the order of1-40% of the total solids, depending upon its compatibility with therest of the constituents of the coating composition when in the finaldry state. The amount of the solvent soluble slip agent used in acoating composition must be such that it will be completely soluble inthe liquid coating composition but will, after removal of the solvent,separate at least partially from the main body of the coating.Preferably it should be present in such quantity that the separate phasewill constitute only a small proportion of the total coating, such as 5%or less.

The wax content of these moistureproofing compositions may vary from0.5%, or 1% to 10%, or more of the total solids content. Usually about4% is stisfactory, although more or less may be found desirable fordifferent purposes. The amount of plasticizer may vary, of course, fromnone at all up to about 40 or 50% of the solids content of thecomposition.

The amount of solvent or solvent mixture may vary according to thecomposition and to the method of application, or purpose desired. Theviscosity of the coating composition may be controlled by the amount ornature of the solvent and may be adjusted easily to adapt the solutionfor coating by brushing, spraying, dipping or any other methods familiarto the art.

Where percentages and proportions of ingredients are referred tothroughout the specification and claims, they are intended to bepercentages by weight, or parts by weight.

The term "modified rosin as used throughout the present specificationand claims is defined as the rosin described and claimed in U. S.Letters Patent to Morton, No. 2,017,866; that is to say, a rosin havinga high melting point, a high molecular weight, and being materiallydecolorized.

The term "Petrex as used throughout the present specification and claimsis defined as the terpinene-maleic anhydride complex comprisingessentially3-isopropyl-6-methyl-3:6-endoethylene-delta-4-tetrahydro-phthalicanhydride (J. Ind. Eng. Chem., XXIX, 21) and marketed as Petrex" resinby the Hercules Powder Co.

The surface conditioning agent of the present invention, whenincorporated in coating compositions for use with transparent,cellulosic wrapping tissue, has been found to give a product which iseminently suited for use upon automatic wrapping machinery. For such useit is necessary that the tightly wound rolls of material supplied foruse upon such machines unwind and deliver the film very smoothly andevenly through the machine. terial have been tightly wound and stored atrelatively high temperatures, it is found that there will be absolutelyno sticking between the surfaces of the fllm, allowing it to unroll withgreat ease and freedom from tears, marred surfaces and other blemishes.It is furthermore essential that such material will pass evenly andsmoothly through the whole course of the wrapping machine withoutadherence to various portions of said machine. Very often, certainheated. elements form a part of such machines, said elements generallybeing used for the formation of heat seal at a certain stage of thewrapping operation. Should the adjacent parts of the machine become warmby conduction or convexion of said heating elements, serious trouble mayresult in the operation of the machine by sticking of the wrap pingtissue to these surfaces. The present invention produces a wrappingtissue which is far less likely to adhere to such surfaces than wrappingtissues previously available.

Where the coated wrapping tissue is in the form of sheets, said sheetsmay be stacked and stored for long periods of time without anyappearance of adhesion between the sheets so stacked. Such sheets may bereadily separated and handled manually or by machinery.

The method and materials of this invention produce an improved surfacewithout adversely affecting clarity to the extent encountered in the useof the previously known insoluble slip agents.

In coating compositions giving moistureproofness, this moistureproofnessis not affected so much by the solvent soluble slip agent as withprevious insoluble slip agents.

The method of the invention has the very important advantage of giving amore uniform distribution of the surface conditioning agent throughoutthe coating bath which results in a far more even distribution in thecoating with the elimination of certain optical defects in thetransparent film. Furthermore, it is possible to filter and purify thebath just before application to the film, making possible a very highgrade product. Such filtration is not possible where the agent added isa dispersed solid so that large, solid particles and impurities thatmight occur in the bath at its later stages of preparation would remainto give trouble in the coating machinery and final product.

Not only may the use of the material be more precisely and rigidlycontrolled, but the disadvantages incident to sedimentation when theprepared bath solution is stored for a period of time, or transferredthrough pipes and under conditions which might cause the flocculationand sedimentation of a solid constituent are avoided.

Even though rolls of such ma- Since many changes and modifications can76 obviously be made from the details of the above description withoutdeparting from the nature and spirit of the invention, it is to beunderstood that the inventionv is not to be limited except as set forthin the following claims.

I claim:

1. A moistureprooflng coating composition containing, dissolved in anorganic solvent, 30% to 70% film-forming ingredient, 0.5% to 10%moistureprooflng agent, and 1% to 40% organic compound containing ametal substituted for a hydroxy hydrogen, said compound having a solu- Ibility oi! at least 1% in toluene at a temperature o1 25 0., and 0.5gram of said compound being at least partially insoluble in 25 c. c.acetone at a temperature of 25 Q, said compound being present insumcient quantity to separate as a' distinct phase after the removal ofthe solvent but in insumcient quantity to substantially impair thetransparency of the coating.

2. A moistureprooflng coating composition containing, dissolved in anorganic solvent, 30% to 70% film-forming ingredient, 0.5% to 10%moistureprooflng agent, and 1% to 40% organic compound containing ametal linked to a carbon atom through an oxygen atom only, said compoundhaving a solubility of at least 1% in toluene at a temperature 01' 25C., and 0.5 gram of said compound being at least partially insoluble in25 c. c. acetone ata temperature of 25 0., said compound being presentin sufficient quantity to separate as a distinct phase after the removalof the solvent but in insufllcient quantity to substantially impair thetransparency of the coating.

3. A moistureprooflng coating composition containing, dissolved in anorganic solvent, 30% to 70% illm-forming ingredient, 0.5% to 10%moistureprooflng agent, 40% to 50% plasticizer, and 1% to 40% metallicsalt of a carboxylic acid, said salt having a solubility of at least 1%in toluene at a temperature of 25 0., and 0.5 gram of said salt being'atleast partially insoluble in 25 c. c. acetone at a temperature of 25 C.,said salt being present in suflicient quantity to'separate as a distinctphase after the removal of the solvent but in insufflcient quantity tosubstantially impair the transparency of the coating.

4. A moistureproofing coating composition containing, dissolved in anorganic solvent, 30% to 70% film-forming ingredient, 0.5% to 10%moistureprooflng agent, and a metallic salt of a carboxylic acid, saidsalt having a solubility of at least 1% in toluene at a temperature of25 C., and 0.5 gram of said salt being at least partially insoluble in25 c. c. acetone at a temperature of 25 0., said salt being present insuflicient quantity to separate as a distinct phase after the removal ofthe solvent but inan amount not to exceed 5%.

5. A moistureproofing coating composition containing, dissolved in anorganic solvent, a filmforrning ingredient, a moistureproofing agent anda metallic salt of a carboxylic acid, taken from the class consisting ofcalcium, magnesium and cadmium butyl phthalates; zinc, barium, magnesiumand calcium lauryl phthalates; calcium and magnesium cyclohexylphthalates; aluminum, titanium, and barium benzoyl benzoates; aluminum,magnesium, zinc, and calcium-cymoyl benzoates; aluminum tolyl benzoate;aluminum xylyl benzoate; aluminum, calcium, manganese, lead, magnesium,barium, cadmium, and strontium rosinates; calcium, aluminum, barium,strontium, and cadmium salts of modified rosin; calthe transparency ofthe coating.

6. A moistureprooflng coating composition containing, dissolved in anorganic solvent, 0. filmforming ingredient, a moistureprooflng agent andthe aluminum salt of modified, high melting point, high molecularweight, decolorized rosin, said salt being present in sufficientquantity to separate as a distinct phase after the removal of thesolvent but in insufllcient quantity to substantially impair thetransparency of the coating.

'7. The thin, flexible, slippery, non-fibrous, transparent sheetprovided with a moistureprooiing coating containing afllm-Iormingingredient, a moistureprooflng agent and, as a slip agent ina phase separate from the main body 01' the coating, an organicsolvent-soluble organic compound containing a metal substitute for ahydroxyl hydrogen, said compound having a solubility of at least 1% intoluene at a temperature of 25 C., and 0.5 gram of said compound beingat least partially insoluble in 25 c. c. acetone at a'temperature of 25C., said compound being present in "insuflicient quantity tosubstantially impair the transparency of the sheet.

8. A thin, flexible, slippery, non-fibrous, transparent sheet providedwith a moistureprooiing coating containing a film-forming ingredient, a

.moistureproofing agent and, as a slip agent in a -coating containing afilm-forming ingredient, a

moistureprooflng agent and, as a slip agent in a phase separate from themain body of thecoating, an organic solvent-soluble organic compoundcontaining a metal linked to a carbon atom through an oxygen atom only,said compound having a solubility of at least 1% in toluene at atemperature of 25 C., and 0.5 gram of said compound being at leastpartially insoluble in 25 c. c. acetone at a temperature of 25 0., saidcompound being present in insufllcient quantity to substantially impairthe transparency of the sheet.

10. A thin, flexible, slippery, non-fibrous, transparent sheet providedwith a. moistureproofing coating containing a film-forming ingredient, amoistureproofing agent and, as a slip agent in a phase separate from themain body of the coating, an organic solvent-soluble metallic salt of acarboxylic acid in' an amount not exceeding 5% of the coating, said salthaving a solubility of at least 1% intoluene at a temperature of 25 C.,and 0.5 gram of said salt being at least partially insoluble in 25 c. c.acetone at a temperature of 25 C.

11. A thin, flexible, slippery, non-fibrous, transparent sheet providedwith a moistureprooiing coating containing a film-forming ingredient, amoistureproofing agent and, as a slip agent in a of calcium,

phase separate from the main body of the coat ing, an organicsolvent-soluble metallic salt of a carboxylic acid taken from the classconsisting magnesium and cadmium butyl phthalates; zinc,,barium,magnesium and calcium lauryl phthaiates; calcium and magnesiumcyclohexyl phthalates; aluminum, titanium, and barium benzoyl benzoates;aluminum, magnesium, zinc, and calcium cymoyl benzoates; aluminum tolylbenzoate; aluminum xylyl benzoate; aluminum, calcium manganese, lead,magnesium, barium, cadmium, and strontium resinates; calcium, aluminum,barium, strontium, and cadmium salts of modified rosin; calcium, zinc,and aluminum salts of Petrex resin; aluminum and calcium salts oflauryl, butyl, and cyclohexyl half esters of Petrex resin; sodiumursolate; magnesium and calcium lauryl maleates or aluminum laurylsebacate, said salt being present in insuflicient quantity tosubstantially impair the transparency of the sheet.

12. A thin, flexible, slippery, non-fibrous, transparent sheet providedwith a moistureproofing coating containing a film-forming ingredient, amoistureproofing agent and, as a slip agent in a phase separate from themain body of the coating, the aluminum salt of modified, high meltingpoint, high molecular weight, decolorized rosin, said salt being presentin insufiicient quantity to substantially impair the transparency of thesheet,

13. The method of producing a thin, flexible, slippery, high sticktemperature, transparent, moistureproof sheet which comprises applyingto a transparent, non-fibrous base sheet a moistureproofing coatingcomposition containing in solution a film-forming ingredient, amoistureproofing agent and an organic compound containing a metalsubstituted for a hydroxyl hydrogen, said compound being present insuflicient quantity to separate as a distinct phase after the removal ofthe solvent but in insufficient quantity to substantially impair thetransparency of the coating, and drying said coating composition wherebyto cause said compound to separate as a distinct phase from the mainbody of the coating.

14. A thin, flexible, slippery, high stick temperature, transparent,moistureproof sheet con sisting of a transparent, non-fibrous base sheetprovided with a moistureproofing coating containing 50%-60%nitrocellulose film-forming ingredient, 0.5% to 10% moistureproofingagent and, as a slip agent in a phase separate from the main body of thecoating, 1%-40% of the aluminum salt of modified, high melting point,high molecular weight, decolorized rosin, said salt being present ininsuilicient quantity to substantially impair the transparency of thesheet but not exceeding of the total coating.

15. The method of producing a thin, flexible, slippery, high sticktemperature, transparent, moistureproof sheet which comprises applyingto a transparent, non-fibrous base sheet a moistureproofing coatingcomposition containing in solution a film-forming ingredient, amoistureproofing agent and 1% to 40% (based on the solids content) of ametallic salt of a carb'oxylic acid, said salt having a solubility of atleast 1% in toluene at a temperature of 25 C., and 0.5 gram of said saltbeing at least partially insoluble in 25 cc. acetone at a temperature of25 C. and drying said coating composition whereby to cause said salt toseparate as a distinct phase from the main body or the coating in anamount not exceeding 5%.

16. A thin, flexible, slippery, non-fibrous, trans- .parent sheetprovided with a moistureproofing coating containing 30 %-70%film-forming ingredient, 0.5%-% moistureproofing agent and, as a slipagent in a phase separate from the main body of the coating, 1%-40%organic solventsoluble single metallic salt of a carboxylic acid in anamount not exceeding 5% of the coating, said salt having a solubility ofat least 1% in toluene at a temperature of 25 C.. and 0.5 gram of saidsalt being at least partially insoluble in 25 c. c. acetone at atemperature of 25 C.

17. A thin, flexible, slippery, non-fibrous, transparent sheet providedwith a. moistureproofing coating containing 30 %-70% film-formingingredient, 0.5%-40% moistureproofing agent and, as a slip agent in aphase separate from the main body of the coating, 1%-40% organicsolventsoluble metallic salt of a carboxylic acid taken from the classconsisting of calcium, magnesium and cadmium butyl phthalates; zinc,barium. magnesium and calcium lauryl phthalates; calcium and magnesiumcyclohexyl phthalates; alumium, titanium, and barium benzoyl benzoates;aluminum, magnesium, zinc, and calcium cymoyl benzoates; aluminum tolylbenzoate; aluminum xylyl benzoate; aluminum, calcium manganese, lead,magnesium, barium, cadmium, and strontium rosinates; calcium, aluminum,barium, strontium, and cadmium salts of modified rosin; calcium, zinc,and aluminum salts of Petrex resin; aluminum and calcium salts oflauryl, butyl, and cyclohexyl half esters oi Petrex resin; sodiumursolate; magnesium and calcium lauryl maleates or aluminum laurylsebacate, said salt being present in insufficient quantity tosubstantially impair the transparency of the sheet but not exceeding 5%of the total coating.

18. A thin, flexible, slippery, non-fibrous transparent sheet providedwith a moistureproofing coating containing 30%-70% film-formingingredient, 0.5 %-10% moistureproofing agent and, as a slip agent in aphase separate from the main body of the coating, 1%-40% of the aluminumsalt of modified, high melting point, high molecular weight, decolorizedrosin, said salt being present in insufficient quantity to substantiallyimpair the transparency of the sheet but not exceeding 5% of the totalcoating.

19. A thin, flexible, slippery, non-fibrous, transparent sheet providedwith a moistureproofing coating containing 52% nitrocellulose of 11.6%nitrogen content, 3% paraffin, 5%-14% modified high melting point, highmolecular weight decolorized rosin, dicyclohexyl phthalate, 15% dibutylphthalate and 1% 10% of the aluminum salt of modified high meltingpoint, high molecular Weight decolorized rosin.

20. A thin, flexible, slippery, non-fibrous, transparent sheet providedwith a moistureproofing coating containing 30 %-70% nitrocellulose,0.5%-

' 10% moistureproofing agent and, as a. slip agent in a phase separatefrom the main body of the coating, 1%-40% aluminum rosinate.

21. A thin, flexible, slippery, non-fibrous, transparent sheet providedwith a moistureproofing coating containing 46% nitrocellulose, 3%paraffin, 15% modified high melting point high mo lecular weightdecolorized rosin, 16% dicyclohexyl phthalate, 16% dibutyl phthalate,and 4% aluminum monohydroxy benzoyl benzoate.

JAMES A. MITCHELL.

